Carnitine is a water-soluble, vitamin-like compound that functions to transport fatty acids across the mitochondria membrane where they undergo β-oxidation to produce energy. Previous research has shown that carnitine is effective in decreasing lipid accretion rate (T. L. Weeden et al., “The Effect of L-Carnitine on Starter Pig Performance and Carcass Composition”, J. Anim. Sci. 69 (Suppl. 1) (1991), 105 (Abstr.); K. Q. Owen et al., “Effect of L-Carnitine and Soybean Oil on Growth Performance and Body Composition of Early-Weaned Pigs”, J. Anim. Sci. 74 (1996), 1612–1619) (hereinafter “Owen et al. (1996)”). However, carnitine may play a greater role in metabolism than just fatty acid transport (K. Q. Owen et al., “Dietary L-Carnitine Suppresses Mitochondrial Branched-Chain Keto Acid Dehydrogenase Activity, and Enhances Protein Accretion and Carcass Characteristics of Swine”, J. Anim. Sci. 79 (2001), 3104–3112. Recent studies have observed increases in the total number of pigs born and born alive by feeding L-carnitine during gestation (R. E. Musser et al., “Effects of L-Carnitine Fed During Lactation on Sow and Litter Performance”, J. Anim. Sci. 77 (1999), 3296–3303 (hereinafter “Musser et al. (1999a)”).
Musser et al. (1999a) fed sows 50 mg/kg of carnitine during lactation and reported minimal differences in farrowing rate, or in total number of pigs born or born alive in three different experiments. In another study, R. E. Musser et al. (“Effects of L-Carnitine Fed During Gestation and Lactation on Sow and Litter Performance”, J. Anim. Sci. 77 (1999), 3289–3295) (hereinafter “Musser et al. (1999b)”) reported that adding L-carnitine to gestating sow diets had no effect on farrowing rate, but showed an increase in number of pigs born alive in the subsequent parity different from the response in our experiments. The authors also reported no differences in farrowing rate or wean to estrus intervals. The sows were only fed carnitine for one gestation period. See also U.S. Pat. No. 6,342,487.
Musser et al. (1999b) also stated that adding carnitine to the gestation diet improved nutrient utilization. This has also been shown in nursery (D. E. Real et al., “Effects of Dietary L-Carnitine on Growth Performance of Nursery Pigs”, J. Anim. Sci., 79 (Suppl. 2) (2001, in press), Abstr.; M. J. Rincker et al., “Effects of Dietary L-Carnitine on Growth Performance and Apparent Nutrient Digestibility in Weaning Pigs”, J. Anim. Sci. 79 (Suppl. 2) (2001, in press), Abstr.) and grow-finishing pigs (K. Q. Owen et al., “The Effect of L-Carnitine Additions on Performance and Carcass Characteristics of Growing-Finishing Swine” J. Anim. Sci. 71 (Suppl. 1) (1993), 62 (Abstr.). Owen et al. (1996) reported decreases in daily fat accretion when adding dietary carnitine, potentially by increasing β-oxidation of fatty acids. Gestating sows are generally fed diets that contain low amounts of fat once a day. After all nutrients from the digestive tract have been absorbed, added carnitine could improve the utilization of lipids from body stores, leaving glucose needed for fetal growth. Additionally, increasing the energy density of the diet has been associated with improvements in ovulation rate (B. Flowers et al., “Endocrine Changes Associated with a Dietary-Induced Increase in Ovulation Rate (Flushing) in Gilts”, J. Anim. Sci. 67 (1989), 771–778). Therefore, by improving the energy status of the sow additional dietary carnitine could improve ovulation rate.
Chromium is a trace mineral that is involved actively in the metabolism of carbohydrates, lipids, proteins, and nucleic acids in the body. Chromium potentiates insulin action by increasing the cellular uptake of glucose and intracellular carbohydrate and lipid metabolism. Studies have shown that feeding chromium in gestation and lactation increases number born alive (M. D. Lindemann et al., “Further Assessment of the Effects of the Supplementation of Chromium from Chromium Picolinate on Fecundity in Swine”, J. Anim. Sci. 73 (Suppl. 1) (1995), 185 (Abstr.) (hereinafter “Lindemann et al. (1995a)”; C. D. Hagen et al., “Effect of Dietary Chromium Tripicolinate on Productivity of Sows under Commercial Conditions”, Swine Health Prod. 8 (2000), 59–63 (hereinafter “Hagen et al. (2000)”).
There have been several studies investigating chromium supplementation in sow diets. M. D. Lindemann et al., “Dietary Chromium Picolinate Additions Improve Gain: Feed and Carcass Characteristics in Growing-Finishing Pigs and Increase Litter Size in Reproducing Sows”, J. Anim. Sci. 73 (1995), 457–465 (hereinafter “Lindemann et al. (1995b)” and Hagen et al. (2000) reported increases in number of pigs born alive with no effects on farrowing rate when adding 200 μg/kg of chromium. Lindemann et al. (1995b) reported this increase in sows over two parities and also reported increases in total number of pigs born, and gestational weight gain. In a follow up study, Lindemann et al. (1995a) reported no improvements in number of pigs born or born alive. Similarly, our study showed no improvements in number born alive, but we did find increases in farrowing rate and tendencies to increase number of stillborn pigs per litter. R. G. Campbell, “The Effects of Chromium Picolinate on the Fertility and Fecundity of Sows under Commercial Conditions”, Proc. 16th Annual Prince Feed Ingredient Conf. (Quincy, Ill.: 1996), 33–38, reported improvements in farrowing rate in two experiments, but not in a third trial. These different responses were attributed to differences in inherent fertility of the herds, as control sows in the third experiment had reproductive performance similar to that of supplemented sows in the first two experiments. The authors also reported, although not statistically different, an increase in number of stillborn pigs per litter.
Chromium has been shown to enhance glucose clearance rate in pigs (E. K. Amoikon et al., “Effect of Chromium Tripicolinate on Growth, Glucose Tolerance, Insulin Sensitivity, Plasma Metabolites, and Growth Hormone in Pigs”, J. Anim. Sci. 73 (1995), 1123–1139). The study by Lindemann et al. (1995b) reported that feeding 200 μg/kg of chromium to sows decreased plasma insulin and insulin to glucose ratio. This would indicate an increase in insulin sensitivity, which has been associated with improvements in fertility and litter size (J. L. Ramirez et al., Influence of Exogenous Insulin Before Breeding on Conception Rate and Litter Size of Sows”, J. Anim. Sci. 75 (1997), 1893–1898).
U.S. Pat. No. 6,303,158 describes using chromium propionate as a dietary supplement to improve the quality of meat of the animal. Specifically, chromium treatment using chromium propionate resulted in significant pork quality responses in pigs fed either low-or high-metabolizable energy diets. Positively affected were increased marbling, reduced moisture in the longissimus dorsi muscle, and reduced purge/drip loss. Additionally, chromium propionate supplementation tended to improve firmness/wetness scores in both low-or high-metabolizable energy diets.
Several references describe supplementing the feed to swine with L-carnitine and chromium: W. T. Cho et al., “Effects of L-Carnitine, Chromium Picolinate with Different Fat Sources on Growth and Nutrient Digestibility in Pigs Weaned at 21 Days of Age” (1999: reprint of Han'guk Ch'uksan Hakhoechi, 41(4)), pp. 445–456, and abstract thereof; M. D. Lindemann et al., “Evaluation of Two Nutritional Technologies for Improving Sow Productivity: Is It the Same Pig?” (Aug. 29, 2001: Presented at the Prince Agri Products Swine Reproduction Symposium, Des Moines, Iowa); B. T. Richert et al., “Determining the Valine Requirement of the High-Producing Lactating Sow” in B. Goodband et al., Ed., Swine Day 1994 (November 1994: Kansas State University), pp. 10–14; C. J. Samland et al., “Effect of L-Camitine and Chromium Nicotinate on the Ovulation and Fertilization Rate of Gilts”, 5 pages. J. W. Smith, II, et al., “The Effects of Dietary Carnitine, Betaine, and Chromium Nicotinate Supplementation on Growth and Carcass Characteristics in Growing-Finishing Pigs” (1994: Journal of Animal Science: Annual Meeting Abstracts, Vol. 72, Suppl. 1, p. 274), Abstract 1054; J. W. Smith, II, et al., “The Effects of Supplementing Growing-Finishing Pig Diets with Carnitine and(or) Chromium on Growth and Carcass Characteristics” in B. Goodband et al.,Ed., Swine Day 1996: Report of Progress 772, (November 1996: Kansas State University Experimental Station), pp. 111–115; A. T. Waylan, “The Effects of Dietary Supplementation of Modified Tall Oil, Vitamin E, Chromium Nicotinate, and L-Carnitine on Pork Quality, Display Color Stability, and Bacon Characteristics” (1997: M. A. Thesis, Kansas State University, Manhattan, Kans.); A. T. Waylan et al., “The Effects of Swine Dietary Supplementation of Modified Tall Oil, Chromium Nicotinate, and L-Carnitine on Longissimus Muscle Quality Characteristics and Display Color Stability” (1999: Journal of Animal Science, Vol. 77, Suppl. 1, p. 50), Abstract #104; A. T. Waylan et al., “Influence of Dietary Supplementation of Modified Tall Oil, Chromium Nicotinate, and L-Carnitine on Pork Chop Display Color Stability, Warner-Bratzler Shear, and Sensory Panel Traits” in B. Goodband et al., Ed., Swine Day 1999: Report of Progress 841 (November 1999: Kansas State University Agricultural Experiment Station and Cooperative Extension Service), pp. 152–155; and A. T. Waylan et al., “Influence of Dietary Supplementation of Modified Tall Oil, Chromium Nicotinate, and L-Carnitine on Bacon Characteristics” in B. Goodband et al., Ed., Swine Day 1999: Report of Progress 841 (November 1999: Kansas State University Agricultural Experiment Station and Cooperative Extension Service), pp. 156–158.
An important factor influencing the productivity of swine operations is the rate of reproduction. Reproductive management includes consideration of growth and metabolism with ovarian function, and adequate energy is required to achieve full reproductive performance. It is known that dietary flushing which requires daily feed intake of sows for approximately two weeks prior to breeding may enhance ovulation rate and is believed to increase litter size.
Such an extended feeding period is costly and, depending on the individual feed intake of every animal, does not work reliably. Also, the impact of varying the feed composition is not clearly understood. Therefore, a need exists for a diet which is cost efficient, predictable, and effective in enhancing the reproductive performance of swine.